U.S. patent application number 16/725097 was filed with the patent office on 2020-07-02 for etching solution, and method of producing semiconductor element.
The applicant listed for this patent is TOKYO OHKA KOGYO CO., LTD.. Invention is credited to Takuya OHHASHI, Mai SUGAWARA, Yukihisa WADA.
Application Number | 20200211856 16/725097 |
Document ID | / |
Family ID | 71123126 |
Filed Date | 2020-07-02 |
United States Patent
Application |
20200211856 |
Kind Code |
A1 |
WADA; Yukihisa ; et
al. |
July 2, 2020 |
ETCHING SOLUTION, AND METHOD OF PRODUCING SEMICONDUCTOR ELEMENT
Abstract
A SiGe compound etching solution for selectively etching a
compound represented by general formula Si.sub.1-xGe.sub.x
(provided that x is 0 or more and less than 1) relative to Si, Ge
and an oxide thereof, the SiGe compound etching solution including
periodic acid and fluoride.
Inventors: |
WADA; Yukihisa;
(Kawasaki-shi, JP) ; SUGAWARA; Mai; (Kawasaki-shi,
JP) ; OHHASHI; Takuya; (Kawasaki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOKYO OHKA KOGYO CO., LTD. |
Kawasaki-shi |
|
JP |
|
|
Family ID: |
71123126 |
Appl. No.: |
16/725097 |
Filed: |
December 23, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09K 13/08 20130101;
H01L 21/30612 20130101 |
International
Class: |
H01L 21/306 20060101
H01L021/306; C09K 13/08 20060101 C09K013/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 2018 |
JP |
2018-244958 |
Claims
1. A SiGe compound etching solution for selectively etching a
compound represented by general formula Si.sub.1-xGe.sub.x
(provided that x is 0 or more and less than 1) relative to Si, Ge
and an oxide thereof, the SiGe compound etching solution comprising
periodic acid and fluoride.
2. The etching solution according to claim 1, further comprising a
pH adjuster.
3. A method of producing a semiconductor element, the method
comprising subjecting an object to be treated containing a compound
represented by general formula Si.sub.1-xGe.sub.x to an etching
treatment using the etching solution according to claim 1.
Description
TECHNICAL FIELD
[0001] The present invention relates to an etching solution, and a
method of producing a semiconductor element.
[0002] Priority is claimed on Japanese Patent Application No.
2018-244958, filed Dec. 27, 2018, the content of which is
incorporated herein by reference.
DESCRIPTION OF RELATED ART
[0003] Conventionally, scaling of the configuration in an
integrated circuit has made it possible to increase the density of
functional units on a semiconductor chip. For example, shrinking
transistor size allows for the incorporation of an increased number
of memory devices on a chip, leading to the fabrication of products
with increased capacity.
[0004] In the manufacture of field effect transistors (FETs) for
integrated circuit devices, Ge is used as a semiconductor crystal
material other than silicon. Ge offers a number of potentially
advantageous features relative to silicon, such as high charge
carrier (hole) mobility, band gap offset, a different lattice
constant, and the ability to alloy with silicon to form
semiconducting binary alloys of SiGe.
[0005] Various etching solutions with high selectivity to Ge
materials (in particular, a compound represented by general
formula: Si.sub.1-xGe.sub.x, wherein x is more than 0 and less than
1; hereafter, sometimes referred to simply as "SiGe compound") have
been proposed.
[0006] For example, Patent Literature 1 describes an etching
composition including at least one diol compound, at least one
fluoride species and at least one oxidizing species.
[0007] Patent Literature 2 describes an etching composition
containing peracetic acid, fluoric acid, and an oxide.
DOCUMENTS OF RELATED ART
Patent Literature
[0008] [Patent Literature 1] Japanese Unexamined Patent Application
Publication (Translation of PCT Application) No. 2018-519674 [0009]
[Patent Literature 2] U.S. Pat. No. 7,176,041
SUMMARY OF THE INVENTION
[0010] However, the conventional etching solution as described in
Patent Document 1 or 2 is chemically unstable, and the etching rate
for the SiGe compound may fluctuate with time, which may make it
difficult to control the manufacturing process.
[0011] The present invention takes the above circumstances into
consideration, with an object of providing an etching solution with
improved etching rate stability over time for a compound
represented by general formula: Si.sub.1-xGe.sub.x, a method of
treating an object using the etching solution, and a method of
producing a semiconductor element.
[0012] For solving the above-mentioned problems, the present
invention employs the following aspects.
[0013] A first aspect of the present invention is a SiGe compound
etching solution for selectively etching a compound represented by
general formula Si.sub.1-xGe.sub.x (provided that x is 0 or more
and less than 1) relative to Si, Ge and an oxide thereof, the SiGe
compound etching solution including periodic acid and fluoride.
[0014] A second aspect of the present invention is a method of
treating an object, the method including subjecting the object to
be treated containing a compound represented by general formula
Si.sub.1-xGe.sub.x to an etching treatment using the etching
solution according to the first aspect.
[0015] A third aspect of the present invention is a method of
producing a semiconductor element, the method including subjecting
an object to be treated containing a compound represented by
general formula Si.sub.1-xGe.sub.x to an etching treatment using
the etching solution according to the first aspect.
[0016] According to the present invention, there are provided an
etching solution with improved etching rate stability over time for
a compound represented by general formula: Si.sub.1-xGe.sub.x, and
a method of producing a semiconductor element.
DETAILED DESCRIPTION OF THE INVENTION
[0017] (Etching Solution)
[0018] The etching solution according to a first aspect of the
present invention includes periodic acid and fluoride. The etching
solution of the present embodiment is used for selectively etching
a compound represented by general formula Si.sub.1-xGe.sub.x
(hereafter, sometimes referred to simply as "SiGe compound")
relative to Si, Ge and an oxide thereof
[0019] <Periodic Acid>
[0020] The etching solution of the present embodiment includes
periodic acid. Examples of the periodic acid include orthoperiodic
acid (H.sub.5IO.sub.6) and metaperiodic acid (HIO.sub.4), and
orthoperiodic acid (H.sub.5IO.sub.6) is preferable.
[0021] SiGe compounds may be rendered soluble by oxidation.
Periodic acid is an oxidant that releases oxygen atoms to oxidize
the SiGe compound, and the redox potential of periodic acid has a
potential sufficient to oxidize the SiGe compound. As a result, a
SiGe compound may be efficiently oxidized.
[0022] The amount of the periodic acid in the etching solution of
the present embodiment is not particularly limited. The amount of
periodic acid with respect to the total mass of the etching
solution is, for example, 0.02 to 5% by mass, preferably 0.05 to
4.5% by mass, more preferably 0.1 to 4% by mass, and still more
preferably 0.20 to 3% by mass.
[0023] When the amount of periodic acid is within the
above-mentioned range, the stability over time of the etching rate
with respect to the SiGe compound may be more reliably
improved.
[0024] <Fluoride>
[0025] The etching solution of the present embodiment contains
fluoride.
[0026] Fluoride species contemplated include, but are not limited
to, hexafluorotitanic acid, hexafluorosilicic acid,
hexafluorozirconic acid, tetrafluoboric acid, tetrabutylammonium
trifluoromethanesulfonate, tetraalkylammonium tetrafluoroborates
(NR.sub.1R.sub.2R.sub.3R.sub.4BF.sub.4) such as tetrabutylammonium
tetrafluoroborate, tetraalkylammonium hexafluorophosphates
(NR.sub.1R.sub.2R.sub.3R.sub.4PF.sub.6) tetraalkylammonium
fluorides (NR.sub.1R.sub.2R.sub.3R.sub.4F) (anhydrous or hydrates
thereof) such as tetramethylammonium fluoride, ammonium bifluoride,
ammonium fluoride, where R.sub.1, R.sub.2, R.sub.3, R.sub.4 may be
the same as or different from one another and is selected from the
group consisting of hydrogen, straight-chained or branched
C.sub.1-C.sub.6 alkyl groups (e.g., methyl, ethyl, propyl, butyl,
pentyl, hexyl), C.sub.1-C.sub.6 alkoxy groups (e.g., hydroxyethyl,
hydroxypropyl) substituted or unsubstitued aryl groups (e.g.,
benzyl).
[0027] Among the above examples, as the fluoride, hydrofluoric acid
(DHF) and/or ammonium fluoride (NH.sub.4F) is preferable.
[0028] In the etching of the present embodiment, as the fluoride,
one kind of compound may be used, or two or more kinds of compounds
may be used in combination.
[0029] The amount of the fluoride in the etching solution of the
present embodiment is not particularly limited. The amount of
fluoride with respect to the total mass of the etching solution is,
for example, 0.02 to 5% by mass, preferably 0.025 to 3.00% by mass,
more preferably 0.03 to 2.50% by mass, and still more preferably
0.04 to 2.00% by mass. When the amount of fluoride is within the
above-mentioned range, the etching rate with respect to the SiGe
compound may be more reliably improved.
[0030] Further, the fluorine ion concentration of the etching
solution of the present embodiment is not particularly limited, but
for example, 0.005 to 2.50 mol/L, preferably 0.007 to 1.50 mol/L,
more preferably 0.008 to 1.25 mol/L, and still more preferably
0.010 to 1.00 mol/L. When the fluorine ion concentration is within
the above-mentioned range, the etching rate with respect to the
SiGe compound may be more reliably improved.
[0031] <Other Components>
[0032] The etching solution of the present embodiment may contain,
in addition to the above components, other components as long as
the effects of the present invention are not impaired. Examples of
other components include water, a water-soluble organic solvent, a
pH adjuster, an oxidizing agent, a passivation agent, and a
surfactant.
[0033] Water
[0034] The etching solution of the present embodiment preferably
contains water as a solvent for the above components. The water may
contain trace components that are inevitably mixed. The water used
in the etching solution of the present embodiment is preferably
water that has been subjected to purification treatment, such as
distilled water, ion-exchanged water, and ultrapure water, more
preferably ultrapure water that is generally used in semiconductor
manufacturing.
[0035] The amount of water in the etching solution of the present
embodiment is not particularly limited, and is preferably 80% by
mass or more, more preferably 90% by mass or more, and still more
preferably 94% by mass or more. The upper limit is not particularly
limited, but is preferably less than 99.95% by mass, more
preferably 99.9% by mass, and still more preferably 99.5% by mass.
The etching solution of the present embodiment is preferably an
aqueous solution containing periodic acid and fluoride.
[0036] Water-Soluble Organic Solvent
[0037] The etching solution of the present embodiment may contain a
water-soluble organic solvent, as long as the effects of the
present invention are not impaired. Examples of the water-soluble
organic solvent include alcohols (such as methanol, ethanol,
ethylene glycol, propylene glycol, glycerin, 1,3-propanediol,
1,3-butanediol, 1,4-butanediol, diethylene glycol, dipropylene
glycol, furfuryl alcohol, and 2-methyl-2,4-pentanediol), dimethyl
sulfoxide, and ethers (such as ethylene glycol dimethyl ether,
diethylene glycol dimethyl ether, triethylene glycol dimethyl
ether, tetraethylene glycol dimethyl ether, propylene glycol
dimethyl ether).
[0038] In the etching of the present embodiment, as the
water-soluble organic solvent, one kind of compound may be used, or
two or more kinds of compounds may be used in combination.
[0039] When the etching solution of the present embodiment contains
water-soluble organic solvent, the amount of the water-soluble
organic solvent, relative to the total amount of water and the
water-soluble organic solvent is preferably 50% by mass or less,
more preferably 30% by mass or less, and still more preferably 10%
by mass or less.
[0040] pH Adjuster
[0041] For further improving the etching rate with respect to the
SiGe compound, the etching solution of the present embodiment may
contain a pH adjuster.
[0042] As the pH adjuster, at least one member selected from the
group consisting of acids and salts thereof is preferable.
Specifically examples thereof include methanesulfonic acid,
trifluoromethanesulfonic acid, oxalic acid dihydrate, citric acid,
tartaric acid, picolinic acid, succinic acid, acetic acid, lactic
acid, sulfosuccinic acid, benzoic acid, propionic acid, formic
acid, pyruvic acid, maleic acid, malonic acid, fumaric acid, malic
acid, ascorbic acid, mandelic acid, heptanoic acid, butyric acid,
valeric acid, glutaric acid, phthalic acid, hypophosphorous acid,
salicylic acid, 5-sulfosalicylic acid, hydrochloric acid,
ethanesulfonic acid, butanesulfonic acid, p-toluenesulfonic acid,
dichloroacetic acid, difluoroacetic acid, monochloroacetic acid,
monofluoroacetic acid, trichloroacetic acid, trifluoroacetic acid,
hydrobromic acid (62% by weight), sulfuric acid, ammonium acetate,
sodium acetate, potassium acetate, tetramethylammonium acetate and
other tetraalkylammonium acetates, phosphonium acetate, ammonium
butyrate, ammonium trifluoroacetate, ammonium carbonate, ammonium
chloride, ammonium sulfate, phosphoric acid, diammonium hydrogen
phosphate, ammonium dihydrogen phosphate, bis(tetramethylammonium)
hydrogen phosphate, disodium hydrogen phosphate, phosphorus sodium
dihydrogen phosphate, dipotassium hydrogen phosphate, potassium
dihydrogen phosphate, ditetraalkyl ammonium hydrogen phosphate,
ditetraalkyl ammonium dihydrogen phosphate, diphosphonium hydrogen
phosphate, phosphonium dihydrogen phosphate, ammonium phosphonate,
tetraalkylammonium phosphonate, sodium phosphonate, potassium
phosphonate, phosphonium phosphonate, etidronic acid, and salts
thereof.
[0043] Among the above examples, as the acid for the pH adjuster,
methanesulfonic acid or oxalic acid is preferable.
[0044] The etching solution of the present embodiment may contain,
as a pH adjuster, a basic compound. As such basic compounds,
organic alkaline compounds and inorganic alkaline compounds can be
used. Preferable examples of organic alkaline compounds include
quaternary ammonium salts including organic quaternary ammonium
hydroxides, and alkylamines and derivatives thereof, such as
trimethylamine and triethylamine.
[0045] Examples of the inorganic alkaline compound include
inorganic compounds containing alkali metals or alkaline earth
metals and salts thereof. Examples thereof include lithium
hydroxide, sodium hydroxide, potassium hydroxide, rubidium
hydroxide and cesium hydroxide.
[0046] In the etching of the present embodiment, as the pH
adjuster, one kind of compound may be used, or two or more kinds of
compounds may be used in combination.
[0047] When the etching solution of the present embodiment contains
a pH adjuster, the amount of the pH adjuster with respect to the
total mass of the etching solution is, for example, 0.01 to 10% by
mass, preferably 0.02 to 4.5% by mass, more preferably 0.03 to 4%
by mass, and still more preferably 0.05 to 3% by mass. When the
amount of the pH adjuster is within the above-mentioned range, the
etching rate with respect to the SiGe compound may be more reliably
improved.
[0048] Oxidizing Agent
[0049] The etching solution of the present embodiment may contain,
in addition to periodic acid, any other oxidizing agent.
[0050] Examples of the oxidizing agent include hydrogen peroxide,
FeCl.sub.3, FeF.sub.3, Fe(NO.sub.3).sub.3, Sr(NO.sub.3).sub.2,
CoF.sub.3, MnF.sub.3, Oxone
(2KHSO.sub.5.KHSO.sub.4.K.sub.2SO.sub.4), iodic acid, vanadium
oxide (V), vanadium oxide (IV, V), ammonium vanadate, ammonium
peroxomonosulfate, ammonium chlorite, ammonium chlorate, ammonium
iodate, ammonium nitrate, ammonium perborate, ammonium perchlorate,
ammonium periodate, ammonium persulfate, ammonium hypochlorite,
ammonium hypobromite, ammonium tungstate, sodium persulfate, sodium
hypochlorite, sodium perborate, sodium hypobromite, potassium
iodate, potassium manganate, potassium persulfate, nitric acid,
potassium persulfate, potassium hypochlorite, tetramethylammonium
chlorite, tetramethylammonium chlorate, tetramethylammonium iodate,
tetramethylammonium perborate, tetramethylammonium perchlorate,
tetramethylammonium periodate, tetramethylammonium persulfate,
tetrabutylammonium peroxomonosulfate, peroxomonosulfuric acid,
ferric nitrate, urea peroxide, peracetic acid,
methyl-1,4-Benzoquinone (MBQ), 1,4-benzoquinone (BQ),
1,2-benzoquinone, 2,6-dichloro-1,4-benzoquinone (DCBQ), tolquinone,
2,6-dimethyl-1,4-benzoquinone (DMBQ), chloranil, alloxan,
N-methylmorpholine N-oxide, and trimethylamine N-oxide.
[0051] In the etching of the present embodiment, as the oxidizing
agent, one kind of compound may be used, or two or more kinds of
compounds may be used in combination.
[0052] When the etching solution of the present embodiment contains
an oxidizing agent, the amount of the oxidizing agent with respect
to the total mass of the etching solution is preferably 0.01 to 10%
by mass, more preferably 0.1 to 7% by mass.
[0053] Passivation Agent
[0054] The etching solution of the present embodiment may contain a
passivation agent for germanium.
[0055] Examples of the passivation agent include ascorbic acid, L
(+)-ascorbic acid, isoascorbic acid, ascorbic acid derivatives,
boric acid, ammonium diborate, borates (eg, ammonium pentaborate,
sodium tetraborate and dibora Acid ammonium), alanine, arginine,
asparagine, aspartic acid, cysteine, glutamic acid, glutamine,
histidine, isoleucine, leucine, lysine, methionine, phenylalanine,
proline, serine, threonine, tryptophan, tyrosine, valine, sodium
bromide, potassium bromide, Rubidium bromide, magnesium bromide,
calcium bromide, and ammonium bromide represented by the formula
NR.sup.1R.sup.2R.sup.3R.sup.4Br (in the formula, R.sup.1, R.sup.2,
R.sup.3 and R.sup.4 may be the same as or different from each
other, and selected from the group consisting of hydrogen, and
branched or straight-chain C.sub.1-C.sub.6alkyl (such as methyl,
ethyl, propyl, butyl, pentyl, and hexyl).
[0056] In the etching of the present embodiment, as the passivation
agent, one kind of compound may be used, or two or more kinds of
compounds may be used in combination.
[0057] When the etching solution of the present embodiment contains
a passivation agent, the amount of the passivation agent with
respect to the total mass of the etching solution is preferably
0.01 to 5% by mass, more preferably 0.1 to 1% by mass.
[0058] Surfactant
[0059] The etching solution of the present embodiment may contain a
surfactant for the purpose of adjusting the wettability of the
etching solution with respect to the target object (object to be
treated). As the surfactant, a nonionic surfactant, an anionic
surfactant, a cationic surfactant, or an amphoteric surfactant may
be used, and these may be used in combination.
[0060] Examples of nonionic surfactants include polyalkylene oxide
alkylphenyl ether surfactants, polyalkylene oxide alkyl ether
surfactants, block polymer surfactants composed of polyethylene
oxide and polypropylene oxide, and polyoxyalkylene distyrenated
phenyl ether surfactants, polyalkylene tribenzylphenyl ether
surfactants, and acetylene polyalkylene oxide surfactants.
[0061] Examples of the anionic surfactant include alkyl sulfonic
acid, alkyl benzene sulfonic acid, alkyl naphthalene sulfonic acid,
alkyl diphenyl ether sulfonic acid, fatty acid amide sulfonic acid,
polyoxyethylene alkyl ether carboxylic acid, polyoxyethylene alkyl
ether acetic acid, polyoxyethylene alkyl ether propionic acid,
alkyl phosphonic acid, and fatty acid salt. Examples of the "salt"
include ammonium salt, sodium salt, potassium salt,
tetramethylammonium salt and the like.
[0062] Examples of the cationic surfactant include a quaternary
ammonium salt surfactant, and an alkyl pyridium surfactant.
[0063] Examples of amphoteric surfactants include betaine
surfactants, amino acid surfactants, imidazoline surfactants, and
amine oxide surfactants.
[0064] The above surfactants are generally commercially available.
As the surfactant, one kind of compound may be used alone, or two
or more kinds of compounds may be used in combination.
[0065] <Object to be Treated>
[0066] The etching solution of the present embodiment is used for
SiGe compound etching, and an object to be treated including SiGe
compound is the target of the etching processing. The object to be
treated is not particularly limited as long as the object includes
SiGe compound and examples thereof include a substrate having a
SiGe compound-containing layer (SiGe compound-containing film) or
the like. The substrate is not particularly limited and examples
thereof include various substrates such as a semiconductor wafer, a
glass substrate for a photomask, a glass substrate for a liquid
crystal display, a glass substrate for a plasma display, a
substrate for a field emission display (FED), a substrate for an
optical disk, a substrate for a magnetic disk, and substrate for a
magneto-optical disk. As the substrate, a substrate used for
semiconductor device production is preferable. In addition to the
SiGe compound-containing layer and the base material of the
substrate, the substrate may have various layers and structures as
appropriate, such as, for example, metal wiring, a gate structure,
a source structure, a drain structure, an insulating layer, a
ferromagnetic layer, a nonmagnetic layer, and the like. In
addition, the uppermost layer on the device surface of the
substrate does not need to be the SiGe compound-containing layer
and, for example, the intermediate layer of the multilayer
structure may be the SiGe compound-containing layer.
[0067] The size, thickness, shape, layer structure, and the like of
the substrate are not particularly limited and may be appropriately
selected depending on the purpose.
[0068] The SiGe compound-containing layer is preferably a layer
containing a SiGe compound, and more preferably a SiGe compound
film. The thickness of the SiGe compound-containing layer on the
substrate is not particularly limited, and may be appropriately
selected depending on the purpose. Examples of the thickness of the
SiGe compound-containing layer include a range of 1 to 500 nm and 1
to 300 nm.
[0069] The etching solution of the present embodiment may be used
for performing fine processing of the SiGe compound-containing
layer in the substrate, may be used for removing SiGe
compound-containing deposits attached to the substrate, and may be
used to remove impurities such as particles from the object to be
treated having the SiGe compound-containing layer on the
surface.
[0070] According to the etching solution of the present embodiment
described above, since periodic acid is included as the oxidizing
agent, it is possible to improve the stability of the etching rate
over time with respect to the SiGe compound. The reason has not
been elucidated yet, since periodic acid is very stable as an
oxidizing agent, but this is presumed that the etching solution of
the present embodiment does not exhibit deteriorated etching rate
over time with respect to SiGe compound. For example, the etching
rate with respect to SiGe compound hardly changes even after the
etching solution of the present embodiment is stored at room
temperature for 3 days or more or 7 days or more. Therefore, it is
presumed that a manufacturing process including an etching process
of SiGe compound may be stably controlled by the etching solution
of the present embodiment.
[0071] (Method of Treating Object)
[0072] A second aspect of the present invention is a method of
treating an object, the method including subjecting the object to
be treated containing a SiGe compound to an etching treatment using
the etching solution according to the first aspect.
[0073] The object to be treated containing a SiGe compound is the
same as defined for the "object to be treated" described above for
the etching solution, and preferable examples thereof include a
substrate having a SiGe compound-containing layer. The method for
forming the ruthenium-containing layer on the substrate is not
particularly limited and it is possible to use known methods.
Examples of such methods include a sputtering method, a chemical
vapor deposition (CVD) method, a molecular beam epitaxy (MBE)
method, an atomic layer deposition (ALD) method, and the like. The
raw material of the ruthenium-containing layer used when forming
the ruthenium-containing layer on the substrate is not particularly
limited, and appropriate selection thereof is possible according to
the film forming method.
[0074] <Step of Subjecting Object to Etching Treatment>
[0075] This step is a step of carrying out an etching process on
the object to be treated containing a SiGe compound, using the
etching solution according to the first aspect, and includes an
operation of bringing the etching solution into contact with the
object to be treated. The etching treatment method is not
particularly limited and it is possible to use a known etching
method. Examples of such methods include a spray method, an
immersion method, a liquid filling method, or the like, without
being limited thereto.
[0076] In the spray method, for example, the object to be treated
is transported or rotated in a predetermined direction, the etching
solution according to the first aspect is sprayed into the space
such that the etching solution is brought into contact with the
object to be treated. If desired, the etching solution may be
sprayed while rotating the substrate using a spin coater.
[0077] In the immersion method, the object to be treated is
immersed in the etching solution according to the first aspect and
the etching solution is brought into contact with the object to be
treated.
[0078] In the liquid filling method, the etching solution according
to the first aspect is placed on the object to be treated and the
object to be treated and the etching solution are brought into
contact with each other.
[0079] It is possible to appropriately select these etching process
methods depending on the structure, materials, and the like of the
object to be treated. In a case of the spray method or the liquid
filling method, it is sufficient if the supply amount of the
etching solution to the object to be treated is an amount by which
the surface to be treated in the object to be treated is
sufficiently wetted by the etching solution.
[0080] The purpose of the etching treatment is not particularly
limited and may be fine processing for a surface to be treated of
the object to be treated containing SiGe compound (for example, a
SiGe compound-containing layer on a substrate), may be removal of a
SiGe compound-containing deposit attached to the object to be
treated (for example, a substrate having a SiGe compound-containing
layer), or may be cleaning of a surface to be treated of the object
to be treated containing SiGe compound (for example, a SiGe
compound-containing layer on the substrate).
[0081] In a case where the purpose of the etching treatment is fine
processing of the surface to be treated of the object to be treated
including SiGe compound, generally, the portion not to be etched is
covered with an etching mask and the object to be treated and the
etching solution are brought into contact with each other.
[0082] In a case where the purpose of the etching treatment is the
removal of SiGe compound-containing deposits attached to the object
to be treated, the SiGe compound-containing deposits are dissolved
by bringing the etching solution according to the first aspect into
contact with the object to be treated and it is possible to remove
the SiGe compound deposits from the object to be treated.
[0083] In a case where the purpose of the etching treatment is to
clean the surface to be treated of the object to be treated
including ruthenium, the surface to be treated is rapidly dissolved
by bringing the etching solution according to the first aspect into
contact with the object to be treated and impurities such as
particles attached to the surface of the object to be treated are
removed from the surface of the object to be treated in a short
time.
[0084] The temperature at which the etching treatment is performed
is not particularly limited as long as the SiGe compound is
dissolved with the etching solution. Examples of the temperature
for the etching process include 15.degree. C. to 60.degree. C. In a
case of any of the spray method, the immersion method, and the
liquid filling method, the etching rate is increased by increasing
the temperature of the etching solution, but it is possible to
appropriately select the processing temperature in consideration of
suppressing composition changes in the etching solution to be
small, or workability, safety, cost, and the like.
[0085] The time for performing the etching treatment may be
appropriately selected according to the purpose of the etching
treatment, the amount of SiGe compound to be removed by the etching
(for example, the thickness of the SiGe compound-containing layer,
the amount of SiGe compound deposits, and the like) and the etching
treatment conditions.
[0086] According to the method of treating an object of the present
embodiment described above, the object to be treated is etched
using the etching solution according to the first aspect containing
periodic acid as an oxidizing agent. Since the etching solution
exhibits highly stable etching rate with respect to the SiGe
compound over time, a manufacturing process including an etching
step of the SiGe compound may be stably controlled.
[0087] (Method of Producing Semiconductor Element)
[0088] A third aspect of the present invention is a method of
producing a semiconductor element, the method including subjecting
an object to be treated containing a SiGe compound to an etching
treatment using the etching solution according to the first
aspect.
[0089] It is possible to perform the step of carrying out an
etching treatment on the object to be treatment including SiGe
compound in the same manner as the method illustrated in the
"Method of treating object" described above. The object to be
treated including SiGe compound is preferably a substrate having a
SiGe compound-containing layer. As the substrate, it is possible to
use a substrate generally used for semiconductor element
production.
[0090] <Other Steps>
[0091] The method of producing a semiconductor element according to
the present embodiment may include other steps in addition to the
etching treatment step described above. The other steps are not
particularly limited and examples thereof include known steps
performed when manufacturing a semiconductor element. Examples of
the steps include a step for forming each structure such as a metal
wiring, a gate structure, a source structure, a drain structure, an
insulating layer, a ferromagnetic layer, and a nonmagnetic layer
(layer formation, etching other than the etching process described
above, chemical mechanical polishing, modification, and the like),
a resist film formation step, an exposure step, a development step,
a heating process step, a cleaning step, an inspection step, and
the like, without being limited thereto. It is possible to
appropriately perform these other steps before or after the etching
process step if desired.
[0092] According to the method of producing a semiconductor element
of the present embodiment described above, an etching treatment for
an object to be treated is performed using an etching solution
according to the first aspect described above including periodic
acid as an oxidizing agent.
[0093] Since the etching solution exhibits highly stable etching
rate with respect to the SiGe compound over time, a manufacturing
process including an etching step of the SiGe compound may be
stably controlled.
EXAMPLES
[0094] As follows is a description of examples of the present
invention, although the scope of the present invention is by no way
limited by these examples.
Preparation of Etching Solution
Examples 1 to 4, Comparative Examples 1 to 3
[0095] The components shown in Table 1 were mixed together to
obtain each etching solution.
TABLE-US-00001 TABLE 1 Oxidizing Solvent Fluoride agent pH adjuster
Comparative Water DHF -- -- Example1 [99.9%] [0.1%] Comparative
Water DHF PAA -- Example2 [98.4%] [0.1%] [1.5%] Comparative Water
NH.sub.4F PAA -- Example3 [98.4%] [0.1%] [1.5%] Example1 Water DHF
PIA -- [98.4%] [0.1%] [1.5%] Example2 Water NH.sub.4F PIA --
[98.4%] [0.1%] [1.5%] Example3 Water NH.sub.4F PIA AA [97.4%]
[0.1%] [1.5%] [1%] Example4 Water NH.sub.4F PIA MSA [97.4%] [0.1%]
[1.5%] [1%]
[0096] In Table 1, the reference characters indicate the following.
The values in brackets [ ] indicate the amount (in terms of parts
by mass) of the component added.
[0097] DHF: hydrofluoric acid
[0098] NH.sub.4F: ammonium fluoride
[0099] PAA: peracetic acid
[0100] PIA: periodic acid (H.sub.5IO.sub.6)
[0101] AA: acetic acid
[0102] MSA: methanesulfonic acid
[0103] <Etching Treatment of Object (1)>
[0104] A SiGe film was epitaxially grown on a silicon substrate to
obtain an object to be treated (1) on which the SiGe film was
formed. A test piece was cut out from the obtained object (1) and
the film thickness of the SiGe film was measured by fluorescent
X-ray analysis. As a result, it was found that the film thickness
was 50 nm.
[0105] The etching solution of each example was put into a beaker,
and an etching treatment was performed by immersing the test piece
in the etching solution of each example for 5 minutes at room
temperature (23.degree. C.). After the etching treatment, the test
piece was dried by nitrogen blowing, and the thickness of the SiGe
film was measured by fluorescent X-ray analysis. The etching rate
(.ANG./min) with respect to SiGe was calculated from the film
thickness of the SiGe film before and after the etching treatment.
The results are shown in Table 2.
[0106] <Etching Treatment of Object (2)>
[0107] A test piece was cut from a SOI (100) substrate to obtain an
object to be treated (2). The film thickness of the Si film on the
obtained object (2) was measured by spectroscopic ellipsometry. As
a result, it was found that the film thickness was 100 nm.
[0108] The etching solution of each example was put into a beaker,
and an etching treatment was performed by immersing the test piece
in the etching solution of each example for 5 minutes at room
temperature (23.degree. C.). After the etching treatment, the test
piece was dried by nitrogen blowing, and the thickness of the Si
film was measured by spectroscopic ellipsometry. The etching rate
(.ANG./min) with respect to Si was calculated from the film
thickness of the Si film before and after the etching treatment.
The results are shown in Table 2.
[0109] <Etching Treatment of Object (3)>
[0110] A silicon oxide film was formed on the silicon substrate by
chemical vapor deposition (CVD) to obtain an object to be treated
(3). A test piece was cut out from the obtained object (3) and the
thickness of the silicon oxide film was measured by spectroscopic
ellipsometry. As a result, it was found that the thickness was 100
nm.
[0111] The etching solution of each example was put into a beaker,
and an etching treatment was performed by immersing the test piece
in the etching solution of each example for 5 minutes at room
temperature (23.degree. C.). After the etching treatment, the test
piece was dried by nitrogen blowing, and the thickness of the
silicon oxide film was measured by spectroscopic ellipsometry. The
etching rate (.ANG./min) with respect to Si was calculated from the
thickness of the silicon oxide film before and after the etching
treatment. The results are shown in Table 2.
[0112] <Evaluation of Etching Selectivity>
[0113] Based on the results of the etching rate obtained in
"Etching treatment of object (1)", "Etching treatment of object
(2)" and Etching treatment of object (3), the etching selectivity
ratio of object (1)/object (2) and the etching selectivity ratio of
object (1)/object (3) were calculated. The results are shown in
Table 2.
TABLE-US-00002 TABLE 2 Etching rate (.ANG./min) Etching selectivity
ratio Object Object Object Object (1)/ Object (1)/ (1) (2) (3)
Object (2) Object (3) Comparative <1 <1 <1 -- -- Example1
Comparative 27.6 3.7 11.5 7.5 2.4 Example2 Comparative 16.7 0.9 2.6
17.8 6.4 Example3 Example1 36.5 4.8 12.2 7.6 3.0 Example2 17.0 1.0
2.7 17.0 6.3 Example3 17.5 0.8 6.0 21.9 2.9 Example4 13.0 0.3 1.4
46.5 9.6
[0114] From the results shown in Table 2, it was confirmed that the
etching solutions of Examples 1 to 4 exhibited about the same level
of SiGe etching selectivity ratio as the etching solutions of
Comparative Examples 1 to 3.
[0115] In particular, the etching solutions of Examples 3 and 4
containing a pH adjuster exhibited improved SiGe etching
selectivity ratio, as compared to the etching solutions of
Comparative Examples 1 to 3.
[0116] <Evaluation of Stability of SiGe Etching Rate Over
Time>
[0117] The etching solution of Example 2 and the etching solution
of Comparative Example 3 were each stored in a bottle, and for each
etching solution 3 days after the start of storage, the etching
rate ER3 (.ANG./min) with respect to SiGe was calculated in the
same manner as in the above "Etching treatment of the object
(1)".
[0118] Further, for each etching solution 7 days after the start of
storage, the etching rate ER7 (.ANG./min) with respect to SiGe was
calculated in the same manner as in the above "Etching treatment of
the object (1)".
[0119] The etching rate obtained in the above "Etching treatment of
the object (1)" was defined as the etching rate ER0 with respect to
SiGe of the etching solution 0 days after start of storage.
[0120] For each of the etching rate ER3 and the etching rate ER7,
the variation rate (%) from the etching rate ER0 was calculated.
The results are shown in Table 3.
TABLE-US-00003 TABLE 3 Comparative Example 3 Example 2 Etching rate
Variation ratio Etching rate Variation ratio (.ANG./min) (%)
(.ANG./min) (%) ER0 16.7 100.0 ER0 17.0 100.0 ER3 11.1 66.7 ER3
17.0 100.0 ER7 7.7 45.8 ER7 16.9 99.4
[0121] As seen from the results shown in Table 3, it was confirmed
that the etching solution of Example 2 hardly varied in the etching
rate with respect to SiGe even after storing for 7 days.
[0122] While preferred embodiments of the invention have been
described and illustrated above, it should be understood that these
are exemplary of the invention and are not to be considered as
limiting. Additions, omissions, substitutions, and other
modifications can be made without departing from the spirit or
scope of the present invention. Accordingly, the invention is not
to be considered as being limited by the foregoing description, and
is only limited by the scope of the appended claims.
* * * * *